Matthew 6:1-4 Beware of practicing your righteousness before other people in order to be seen by them, for then you will have no reward from your Father who is in heaven.
Thus, when you give to the needy, sound no trumpet before you, as the hypocrites do in the synagogues and in the streets, that they may be praised by others. Truly, I say to you, they have received their reward. But when you give to the needy, do not let your left hand know what your right hand is doing, so that your giving may be in secret. And your Father who sees in secret will reward you.
The Bible mentions rewards in several places. What we do during our earthly life has eternal implication. We will earn rewards that we will reap throughout eternity – both good and bad.
Practicing righteousness is a good thing. Giving to the poor is commendable, even commanded in the Bible. When you do these things, you will receive a reward. Not only will you receive a reward, but you get to choose when and where you will receive it.
If you do your good works in obedience to God, then He will reward you, possibly in this life, and definitely in eternity. God reserves the glory for Himself. So, if you do your good work in a manner that only God receives the glory, He is pleased and will honor your good work.
If you do your good work in a manner that you receive the glory, well then, the glory you receive is your reward. This is not a sin issue. It is never a sin to do good works. Your attitude might be sinful (i.e., prideful), but the work itself is good. However, you have received the glory or praise from men, or thanks from the recipient and that is all you will get.
The reward you would receive from God will be significantly better than anything you will receive from men, so it is better to do good works secretly and let your reward come from God.
Lord God, thank You for the opportunities You provide for me to bless others by doing good works. Please guide me in those works and show me how to do them in the manner that gives You the most praise and glory.